Daniel Fahrenheit, Anders Celsius Left Their Marks

It's deep, dark winter, time to pay homage to Alaskans' favorite scientific instrument--the centrifuge.

No, I'm kidding. Our favorite scientific instrument, the thermometer, hangs from every Alaska dwelling from Attu to Anaktuvuk Pass, even a few outhouses. In a shared winter ritual, we check our beloved thermometers thousands of times a day.

But what are we looking at? What's the deal with this Fahrenheit and Celsius stuff?

If they hadn't died, you could ask Daniel Fahrenheit and Anders Celsius, two 18th-century scientists whose names stuck with temperature scales that stuck on our thermometers. Fahrenheit and Celsius were both northerners: Fahrenheit spent much of his life in Amsterdam; Celsius was from Sweden.

Both men lived at the same time, but there's no evidence that they met one another. Fahrenheit was 15 years older than Celsius, but they both lived during a time of great scientific opportunity in Europe.

Fahrenheit's parents both died in 1701 when he was 15. His guardian then sent him to Amsterdam to study business. The young Fahrenheit became fascinated with scientific instruments. He bounced around Europe, learning from scientists and craftsmen in different cities. In his wanderings, he met Olaus Roemer, a Danish astronomer, in Copenhagen.

Though thermometers had existed for more than a century, Roemer developed one very similar to the one we use today. Instead of mercury, Roemer used alcohol, in the form of wine, as the inner liquid that responded to temperature changes. Roemer's thermometer had two reference points: he chose 60 degrees as the temperature of boiling water and 7 1/2 degrees as the temperature of melting ice.

Fahrenheit, no fan of "inconvenient and awkward fractions," according to his letters, modified Roemer's scale. He divided each degree into four parts and used mercury rather than wine.

Fahrenheit established three fixed points on his thermometer. Zero degrees was the temperature of an ice, water, and salt mixture. When he omitted salt from the slurry, he reached his second fixed point when the water-ice combination stabilized at "the thirty-second degree." His third fixed point was "found as the ninety-sixth degree, and the spirit expands to this degree when the thermometer is held in the mouth or under the armpit of a living man in good health."

After Fahrenheit died in 1736, scientists calibrated his model of thermometer using 212 degrees, the temperature at which water boils, as the upper fixed point. When the Fahrenheit thermometer was recalibrated, normal human body temperature registered 98.6 rather than 96.

This post-Fahrenheit version of the Fahrenheit scale is now used in America, but most of the world prefers the scale named after Anders Celsius.

Celsius was an astronomer who was born in Uppsala, Sweden in 1701 and died there 43 years later. Had he not dabbled in thermometry, Celsius might have been known for his collection of aurora borealis observations he published in Nuremburg, Germany, in 1733.

A 100-degree scale had been used before Celsius began experimenting with thermometers, but it was his paper, "Observations on two persistent degrees on a thermometer" that earned his monogram a spot on everyone's thermometer.

In the paper, published two years before his death, Celsius established two fixed points on his thermometer. Zero represented the boiling point of water and 100 was the temperature at which water froze. Celsius' scale doesn't make intuitive sense now, and it apparently didn't when he developed it. After he died, his scale was inverted to what we know now as the Celsius scale, with zero representing the freezing point of water at standard atmospheric pressure and 100 the boiling point.

The centigrade scale Celsius introduced was accepted first in Sweden and France. Soon, people across the globe began using it. Celsius wasn't immortalized until 1948, when the Ninth General Conference of Weights and Measures declared "degrees centigrade" should thereafter be referred to as "degrees Celsius."

Not bad for a guy who would have told you your morning coffee was zero degrees.